In view of the recent trend of power cost reduction, effective utilization of natural resources, and global warming prevention, the consideration has been made with respect to effective utilization of the byproduct gas as the fuel, for example, the coke oven gas discharged from iron works and the off-gas discharged from oil refinery. In the integrated coal gasification combined cycle power generation plant (IGCC) which generates electricity by gasifying coal of rich resources, consideration has been made for means for reducing CO2 emissions by the use of the system for capturing and storing carbon in the gas fuel (Carbon Capture and Storage or CCS).
The gas fuel including the aforementioned byproduct gas and coal-derived syngas from IGCC contains hydrogen (H2) and carbon monoxide (CO) as the main component, the flame speed of which is higher than that of the natural gas (containing methane as the main component) generally used for the gas turbine. As a result, the high temperature flame is generated around the wall surface inside the combustion chamber, causing the risk of deteriorating reliability of the combustor. As an effective method for preventing local generation of the high temperature flame, the fuel is dispersed to ensure homogeneous combustion in the combustion chamber.
JP 2003-148734 discloses an exemplary gas turbine combustor configured to prevent generation of the high temperature flame by enhancing the fuel dispersibility to reduce emissions of NOx. The gas turbine combustor includes a plurality of fuel nozzles and air holes and a plurality of burners for injecting the fuel jet and the air jet generated around the fuel jet into the combustion chamber.
In the case of using the aforementioned byproduct gas and the coal-derived syngas from IGCC as the fuel in the gas turbine combustor, the method of operating gas turbine to be described below will be employed for safety purposes upon ignition. Firstly, the startup fuel which contains no hydrogen (for example, oil fuel) is used for ignition. In the operation under the part-load condition, the fuel is switched from the startup fuel to the gas fuel. Then, operation is further continued to reach the base load while controlling the number of burners for combusting the gas fuel. Once the base load is reached, the gas turbine is operated under the base-load condition. As the gasifier in the IGCC plant generates the coal-derived syngas using steam generated by waste heat from the gas turbine, the gas turbine has to be started up with the startup fuel other than the coal-derived syngas through the aforementioned operating method.
It is apprehended that pressure fluctuation occurs inside the combustor of the gas turbine to be operated through the aforementioned operating method in the process of increasing the load from the operation under the part-load condition to the operation under the base-load condition after switching the fuel from the startup fuel to the gas fuel. The pressure fluctuation may cause the risk of deteriorating structure reliability of the gas turbine combustor and limiting the load range that allows operation of the gas turbine under the load that cannot be increased to reach the base-load condition.
An object of the present invention is to provide a gas turbine combustor configured to prevent the pressure fluctuation in the process of increasing the load from the operation under the part-load condition to the operation under the base-load condition with respect to the gas fuel that contains hydrogen and carbon monoxide so as to sufficiently ensure the structure reliability and the load range that allows operation of the gas turbine.